Time division multiple access (TDMA) systems are being developed for digital mobile and portable radio systems. These TDMA systems can greatly simplify radio hardware and can accommodate variable user data rates.
However, the large number of overhead symbols required to recover carrier phase in burst-mode operation will often result in a significant reduction in spectral efficiency, nullifying the advantages obtained with the use of TDMA.
The present invention uses a new and elegant digital signal processing technique for performing carrier phase recovery. The technique of the invention is completely digital resulting in circuitry that is greatly simplified and which lends itselt to low-power VLSI implementation.
The inventive technique allows for the demodulation of isolated bursts on the order of 100 symbols in length with no overhead penalty for coherent carrier recovery.
The invention eliminates the requirement for multiplication in the processing of the data.
Frequency offset estimation is uniquely fed forward to the carrier recovery phase of the processing.
Bursts are assumed to arrive in known time slots with a few symbols of uncertainty in position. The ends of the burst need not be determined in the coherent demodulation of this invention, since the demodulation process is initiated in the middle of the burst with demodulating being accomplished outwardly towards the edges of the signal.